Shares in India's Natco Pharma Ltd surge 6 percent after prospects for its generic version for Teva Pharmaceutical Industries' billion dollar drug got a boost from a favourable US court ruling on Wednesday.

An US Supreme Court justice on Wednesday declined a request from Teva for a stay of an appeals court ruling that would strip the company's $4 billion-a-year multiple sclerosis drug Copaxone of patent protection in 2014, rather than in 2015.

In July, the US Court of Appeals for the Federal Circuit issued a decision in a patent fight that pits Teva against two teams developing cheaper generic forms of Copaxone: one with Novartis AG and Momenta Pharmaceuticals Inc ; and another between Mylan Inc and Natco Pharma.